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strouhal number

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Old   February 25, 2008, 02:52
Default strouhal number
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Deloat
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Hi,

Does anyone knows how to find the Strouhal number in Post-CFX? I am modelling constant flow past a cylinder, and wants to figure out the Strouhal number of that flow?

Any ideas guys? Thanks a lot.

Deloat
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Old   February 25, 2008, 06:08
Default Re: strouhal number
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andy20
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Just plot a chart of pressure behind the cylinder vs. time and estimate the period of the variation? Use that to compute the shedding frequency. I assume you know the radius and velocity already - so together that should allow you to compute the Strouhal number. I don't think there's much more to it....

(By the way be careful to account for the fact that with alternate vortex shedding from each side of the cylinder, the frequency of the drag force variation is twice that of the lift force variation...)

Good luck, Andy
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Old   February 25, 2008, 07:02
Default Re: strouhal number
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Rogerio Fernandes Brito
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Trying using Origin 7.5 software to extract this frequency!
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Old   February 25, 2008, 10:23
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Dre
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What I do is plot the vorticity and set the scale so I can see the vortex better. Then I do an animation and export the frames as images. Then all I have to do is match 2 frames. Since my timesteps are constant, I have the time between two identical frames.
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Old   February 27, 2008, 15:11
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pasu
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I believe Strouhal number is only used when the flow is oscillatory. If you are modeling with constant flow then it wont help.
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Old   March 11, 2008, 04:19
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wake
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dear pasu

But there is a defenition of strouhal number for constant flow also the frequency as vortex shedding frequency and diameter as length scale for a given velocity.

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